Changes in the range of dragonflies in the Netherlands and the possible role of temperature change

Abstract

T e trends of 60 Dutch dragonfl y species were calculated for three diff erent periods (1980–1993, 1994– 1998 and 1999–2003). Comparing period 1 and period 3 shows that 39 of these species have increased, 16 have remained stable and 5 have decreased. T ese results show a revival of the Dutch dragonfl y fauna, after decades of ongoing decline. T e species were categorized in diff erent species groups: species with a southern distribution range, species with a northern distribution range, species of running waters, species of fenlands and species of mesotrophic lakes and bogs. T e trends of these diff erent species groups were compared with the all-species control group. As expected, a signifi cantly higher proportion of the south- ern species show a positive trend than the all-species group. In the northern species group on the contrary, a signifi cantly higher proportion of the species show a negative trend than the all-species group. Diff erent explanations for these results are discussed, such as climate change, improved quality of certain habitats and degradation of other habitats. It is likely that the observed increase of southern species is at least partly caused by the increasing temperatures. T e less positive picture of the northern species group is probably more infl uenced by other environmental factor than directly by climate change. T ree out of six southern species which have become established since 1990 have done so during the aftermath of large invasions. It is concluded that dragonfl ies are well capable of using changing climate circumstances to colonise new habitats.